Field of the Disclosure
This disclosure relates to turbochargers with Variable Turbine Geometry (VTG) in combination with a wastegate assembly. More particularly, this disclosure relates to actuating VTG guide vanes as well as a wastegate valve for controlling exhaust gas flow to a turbine wheel, such as with a common actuator.
Description of Related Art
Advantages of turbocharging include increased power output, lower fuel consumption, reduced pollutant emissions, and improved transient response. The turbocharging of engines is no longer primarily seen from a high-power performance perspective, but is rather viewed as a means of reducing fuel consumption and environmental pollution on account of lower carbon dioxide (CO2) emissions. Currently, a primary reason for turbocharging is using exhaust gas energy to reduce fuel consumption and emissions. In turbocharged engines, combustion air is pre-compressed before being supplied to the engine. The engine aspirates the same volume of air-fuel mixture as a naturally aspirated engine, but due to the higher pressure, thus higher density, more air and fuel mass is supplied into a combustion chamber in a controlled manner. Consequently, more fuel can be burned, so that the engine's power output increases relative to the speed and swept volume.
In exhaust gas turbocharging, some of the exhaust gas energy, which would normally be wasted, is used to drive a turbine. The turbine includes a turbine wheel that is mounted on a shaft and is rotatably driven by exhaust gas flow. The turbocharger returns some of this normally wasted exhaust gas energy back into the engine, contributing to the engine's efficiency and saving fuel. A compressor, which is driven by the turbine, draws in filtered ambient air, compresses it, and then supplies it to the engine. The compressor includes a compressor wheel that is mounted on the same shaft so that rotation of the turbine wheel causes rotation of the compressor wheel.
Turbochargers typically include a turbine housing connected to the engine's exhaust manifold, a compressor housing connected to the engine's intake manifold, and a center bearing housing coupling the turbine and compressor housings together. The turbine housing defines a volute that surrounds the turbine wheel and that receives exhaust gas from the engine. The turbine wheel in the turbine housing is rotatably driven by a controlled inflow of exhaust gas supplied from the exhaust manifold.